Chapter 5 Organizing The Elements

1
Chapter 5 Organizing The Elements
2
OBJECTIVES

• Describe how Mendeleev arranged the elements in
  his table
• Explain how the predictions Mendeleev made and
  the discovery of new elements demonstrated the
  usefulness of his periodic table
• Describe the arrangement of elements in the
  modern periodic table
• Explain how the atomic mass of an element is
  determined and how atomic mass units are defined

3

• Identify general properties of metals, nonmetals,
  and metalloids
• Describe how properties of elements change across
  a period in the periodic table
• Relate the number of valence electrons to groups
  in the periodic table and to properties of
  elements in those groups
• Predict the reactivity of some elements based on
  their locations within a group
• Identify some properties of common A group
  elements

4

• In 1750 scientists had identified only 17
  elements most of these were metals
• As the number of identified elements grew so did
  the need for organization
• In 1789 Antoine Lavoisier grouped elements
  according to categories called metals,
  non-metals, gases and earths

5

• In 1860 Mendeleev (Russian) needed to describe
  the now known 63 elements to his students
• On cards, he listed the name, mass and properties
  of the 63 elements
• He arranged them in order of increasing atomic
  mass. He was able to break the elements into
  rows (see pg 127 Fig. 3 and columns based on the
  properties of the elements

6

• Columns increased from TOP to BOTTOM
• He knew that not all elements were discovered yet
  so he left room for them
• Properties of elements are related to its
  location in the table
• Review questions 1-5 pg. 129

7
5.2 Modern Periodic law

• In the modern periodic table, elements are
  arranged by increasing ATOMIC NUMBER (number of
  protons)
• PERIODS
• Each row in the periodic table is a period
• Ex. Period 1 has 2 elements period 2 and 3 have 8
  elements
• The number of elements in each period varies
  because of the available orbitals increase from
  energy level to energy level

8

• In other words---------the first energy level has
  only 1 orbital so, the 1 electron in a H atom
  and the 2 electrons in a He atom can fit in this
  orbital
• But Li contains 3 electrons---------so 2 can fit
  in the 1st orbital and the other electron has to
  go in the 2nd orbital(or energy level) this is
  why Li is the first element in Period 2

9

• Na (sodium) the first element in period 3 has one
  electron in its 3rd orbital or energy level
• K (potassium), the first element in Period 4 has
  one electron in its 4th orbital
• This pattern applies to all elements in the first
  column on the table

10

• GROUPS (FAMILIES)
• Each COLUMN is called a group or family
• The elements within a group have similar
  properties (electron configurations)
• The electron configuration determines the
  chemical properties
• THE PATTERN OF REPEATING CHEMICAL PROPERTIES IS
  CALLED PERIODIC LAW
• REFER TO FIG. 7 PGS 132-133

11

• Atomic Mass
• Copy Fig. 8 into your notebook
• There are 4 pieces of information for each
  element
• Name of the element, its symbol, its atomic
  number, and its atomic mass(the number of
  isotopes and their mass in nature)
• Atoms of 2 isotopes have different atomic
  masses(isotopes have different of neutrons than
  protons) they are usually equal

12
Classes of Elements

• Solids, liquids, gases based on their state at
  room temperature
• Symbols solids (black) liquid (purple) gas
  (red)
• Elements are divided into those that occur
  naturally and those that do not
• Ex. Elements with an atomic number of 93 or
  above DO NOT OCCUR NATURALLY
• 1-92 occur naturally

13

• Third classification is based on general
  properties
• Metalslocated on left (blue)
• Non-metals located on right (yellow)
• Metalloids located in the middle (green)

14

• METALS
• Majority of elements are metals
• Represented by blue boxes
• Good conductors of heat
• Electric current
• Solid at room temperature (except mercury)
• Most are malleable
• Many are ductile (able to be drawn into thin
  wire)

15

• Groups 3 through 12 are referred to as transition
  metals
• These transition metals form a bridge between the
  elements on the left and right
• One property of these metals is their ability to
  form compounds with distinct colors
• Ex. Tinted glass
• They are among the 1st elements discovered

16

• NONMETALS
• Represented by yellow boxes
• Have properties opposite to those of metals
• Poor conductivity of heat and electric
• Low boiling points
• Many are gases at room temperature
• Are brittle (will shatter or crumble)

17

• METALLOIDS
• Represented by green boxes
• Properties of these elements fall somewhere
  between metals and nonmetals
• Their ability to conduct heat or electric depends
  on their temperature

18
Variation across a Period

• Changes in the properties of elements change in a
  similar way when you move from left to right
  (except for period 1)
• From left to right, elements become less metallic
  and more nonmetallic
• Most reactant elements or on the left side of the
  table
• Most reactive nonmetals are on the right side
  (group 17)
• Copy fig. 13 into your notebooks
• Complete questions 1-5 and 7

19

• Valence electrons
• An electron that is in the highest occupied
  energy level of an atom
• Valence electrons play a key role in chemical
  reactions
• The properties of elements vary because the
  number of valence electrons increases from left
  to right

20

• Remember that elements in a group have similar
  properties because they have the same number of
  valence electrons
• Ex. Hydrogen and Lithium have I valence electron

21

• Alkali metals elements in group 1A
• 1 valence electron
• Highly reactive
• Ex. Sodium chloride (table salt)
• Group 1A Li, Na, K, Rb, Cs, Fr
• Their reactivity increases from TOP TO BOTTOM

22

• Alkaline Earth metals
• Group 2A
• Contain 2 valence electrons
• Harder than metals in group 1A
• Differences in reactions with water
• Calcium and magnesium are essential to biological
  functions

23

• Magnesium
• Key role in photosynthesis
• Mixture of magnesium and other metals can be as
  strong as steel but much lighter
• Calcium
• Keeps bones and teeth strong, toothpastes may
  contain calcium to polish teeth
• Plaster casts contain calcium sulfate

24

• The Boron Family
• Group 3A
• Contain 3 valence electrons
• Aluminum(metal) most abundant metal in the
  earths crust
• Boron(metalloid)

25

• The Carbon Family
• Group 4A
• 4 valence electrons
• Contains 1 nonmetal(carbon)
• 2 metalloids(silicon, germanium)
• 2 metals(tin, lead)
• Life on earth would not exist without carbon,
  most compounds in your body contain carbon
• Silicon is the 2nd most abundant element in the
  crust

26

• The Nitrogen family
• Group 5A
• Contain 5 valence electrons
• Contain 2 nonmetals(arsenic, antimony)
• 1 metal(bismuth)
• 1 nonmetal gas (nitrogen)
• 1 solid nonmetal(phosphorus)
• In this group phosphorus and nitrogen are most
  important
• Contained in fertilizers and compounds in your
  body to release energy

27

• The Oxygen family
• Group 6A
• Contain 6 valence electrons
• 3 nonmetals (oxygen, sulfur, selenium)
• 2 metalloids (tellurium, polonium)
• Oxygen is the most abundant element in the
  earths crust
• Can be stored as a liquid, under pressure
• Ozone is another form of oxygen ground level is
  an eye irritant, in the atmosphere absorbs
  radiation

28

• The Halogens
• Group 7A
• 7 valence electrons
• Highly reactive nonmetals
• 2 gases (fluorine, chlorine)
• 1 liquid (bromine)
• 1 solid (iodine)
• All react easily with most metals

29

• Fluorine compound used to prevent tooth decay,
  non-stick coatings
• Chlorine is in bleach, and used to kill bacteria
  in drinking water and pools (bromine for hot
  tubs)
• Your body needs iodine to keep your thyroid gland
  working properly

30

• The Noble Gases
• Group 8A
• 8 valence electrons (except helium) (2)
• This means these elements have a full outer shell
• This group does not react with any other elements
• Questions 1-10 page 145
• Internet activitysee if you can find the 25
  essential elements to the human body and 3
  elements that should be avoided completely